1a. Objectives (from AD-416)
The overall goal of research is to identify chemical and hydrologic processes controlling nutrient export at farm and watershed scales, locate where they occur on the landscape, quantify what changes occur during transport in stream to receiving waters, and develop, implement, and assess cost-effective Best Management Practices (BMPs) control of nutrient export at farm and watershed levels. Specific objectives are: 1. Quantify impacts of current and alternative fertilizer, manure, crop, and grazing management practices on nutrient cycling within soils at point and field scales. Effective June 15, 2007, research on Objective 1.3: “Quantify NH3 and N2O emissions from urine deposition during grazing” was terminated, and this effort was redirected to Objectives 3.2 and 3.3. 2. Evaluate landscape-scale controls on nutrient transfers to quantify aggregate N and P losses from farming systems and watersheds typical of the Northeast. 3. Identify and quantify processes occurring in the stream channel that control the transfer of nutrients lost from the farm to lakes, reservoirs, and estuaries. Effective June 15, 2007, resources previously allocated to Objective 1.3 were redeployed to accelerate work on Objectives 3.2: “Selecting chemical amendments to reduce P mobility in terrestrial and aquatic systems” and Objective 3.3: “Control nutrient export from ditch drained agriculture” with a focus on the use of industrial byproducts coupled with drainage practices in agricultural and urban landscapes to minimize impact on water quality within the Chesapeake Bay watershed. 4. Determine effectiveness of BMPs in the Cannonsville/Town Brook Watershed and other appropriate watersheds (CEAP-related). 5. Develop, enhance, and apply models and user-oriented indices at field, farm, and watershed scales to evaluate BMPs and N and P export from watersheds.
1b. Approach (from AD-416)
Most of the proposed research will be conducted at three sites in the Northeast U.S.: Mahantango Creek Watershed, PA; Town Brook Watershed, NY; and Manokin River Watershed, MD (Figure 3). These sites are located in agriculturally important areas of the Northeast and reflect the local land use practices. We already have established contacts with landowners at each site and have developed an infrastructure for routine measurement and chemical sampling of surface runoff, subsurface flow, and streamflow. Lease agreements already in place make it easy for us to change management and/or implement alternative practices for cause-and-effect studies on water quality impacts. Also included in this section is a description of the National P Research Project (NPRP) rainfall simulation protocol. Experimental design will vary as a function of each specific research objective and site characteristics. In all cases, appropriate experimental design and statistical analyses will be used.
3. Progress Report
Objective 1. Manure and fertilizer management research involved field trials (runoff, leaching and volatilization measurements) and greenhouse studies (runoff and leaching). Trials with a new ARS poultry litter applicator showed it lower surface runoff of phosphorus by nearly 40% while trials with a new “anti-leaching” liquid manure injector lowered phosphorus leaching levels on sandy soils to 20% less that a control receiving no manure. Crop nitrogen sensor testing confirmed the potential to significantly nitrogen fertilization via variable rate applications using sensor-derived response curves. Objective 2. Research activities included testing rare earth tracers, establishing new field sites to discriminate between nutrient transport pathways, and analyzing soil samples to develop sediment source signatures. Surface runoff and leaching trials with rare earth elements showed them to be excellent labels of particulate phosphorus from manure. Objective 3. Fluvial research was concentrated at the Princess Anne, MD field site. Long-term trends in arsenic transfers reveal that point sources of poultry litter are a primary source of arsenic in ditch flow. Two ditch filters designs show promise in removing phosphorus from ditch water under low flow conditions, with one filter also removing arsenic. Objective 4. CEAP activities continued under the cropland initiative, with the transfer of five more flow years of Mahantango Watershed data to the STEWARDS database. New activities were begun as part of the CEAP wetlands initiative, coordinating phosphorus-related assessments of eastern wetlands. Objective 5. Continued with model assessments of manure application strategies as the farm scale. Long-term data were collected from a rationally grazed beef operation in Pennsylvania that employs swine manure as a primary pasture fertilizer source. Integrated Farming Systems Model runs were conducted to compare manure application technologies intended for use in permanent forages. Efforts were also made to parameterize the model to evaluate farm-scale costs and benefits of adoption a novel USDA-ARS poultry litter applicator on farms in Brazil’s cerrado region.
1. Nitrogen sensor lowers need for fertilizer use on Pennsylvania corn fields: Up to 70% of nitrogen fertilizer applied to corn can be lost to the environment. A novel canopy reflectance sensor enables precision application of the correct amount of nitrogen fertilizer variably across a field to meet the needs of a growing corn crop. Results from fields across Pennsylvania showed a potential to improve nitrogen fertilizer applications by 16% relative to the best of conventional methods, improving farmers’ net return on valuable fertilizer dollars and reducing environmental impact. In addition, this method provides an instantaneous assessment of crop nitrogen status during fertilizer application, a “turnkey” feature that makes this technology more attractive than other testing technologies, increasing the likelihood of farmer adoption.
2. Legacy nutrients from past manure application can delay water quality improvements: To protect and enhance the nation’s water resources, manure management strategies shift land application of manures from riparian areas prone to runoff. Research in the USDA ¬ARS Mahantango Watershed in Pennsylvania reveals that under the right hydrologic conditions, riparian buffers that are properly managed by today’s standards can continue to lose significant quantities of nutrients such as phosphorus, much more than adjacent fields that continue to be fertilized with manure. To overcome this legacy of past practices, additional steps are required such as improving buffer effectiveness with amendments that bind legacy nutrients.
3. Phosphorus leaching losses can be controlled with well-placed tillage: Keeping phosphorus in land applied manure from leaching to tile drains or to near by ditches is a major water quality concern. A new manure injection technology with special features to minimize liquid manure leaching was tested on Maryland’s Eastern Shore. Phosphorus leaching losses were lowered by more than 40% with the new technology relative to conventional methods. The technology was so effective that leaching losses were even lower than those measured on soils that were not fertilized with manure. Results demonstrate the potential to readily manage environmental losses of manure nutrients with new manure application technologies.
Henry, A., Kleinman, P.J., Lynch, J.P. 2008. Phosphorus runoff from a phosphorus deficient soil under common bean (Phaseolus vulgaris L.) and soybean (Glycine max L.) genotypes with contrasting root architecture. Plant and Soil Journal. Available: http://www.springer.com/life+sci/plant+sciences/journal/11104.